Many direct fuel-injection reciprocating piston internal combustion engines depend upon gas motion generated during the compression process for the mixing of air and fuel to enhance the combustion process and to improve air utilization. However, because of the wide operating range demanded of engines in applications such as vehicles, the combustion chamber configuration selected represents a compromise for conventional fixed geometry engines.
Many schemes exist for enhancing cylinder combustion conditions by varying the intake flow passage configuration; see, for example, my U.S. Pat. No. 4,539,954 granted Sept. 10, 1985 to the assignee of the present invention. Also, proposals have been made for varying fuel nozzle flow passages as in my U.S. Pat. No. 4,096,995 granted June 27, 1978 to the assignee of the present invention. However, alterations in combustion chamber geometry during engine operation in response to abrupt changes in operating conditions can be challenging because of the periodic exposure to high temperatures and pressures, the limited space available for control hardware, the need for rapid response and the possibility of adversely compromising the combustion chamber shape.